用waitpid发现的一个疑似内核bug的问题

eagerbever_m

程序简介：父进程创建子进程,子进程中跑实际的应用程序,子进程正常情况下不会退出。父进程负责监视子进程，如果发现其退出则需要重启之。
问题描述：waitpid返回非0，且errno=10, 意思是No child processes, 但实际上此时子进程并未退出，还在sleep中。很奇怪的现象。

/* to monitor if or not my application has exited, if yes, recreate it */
int main()
{
    char apppath[1024];
    char *appname;
    pid_t appId;
    pid_t c_pid;
    int ret;
    sprintf(apppath,"%s","/test/myapp");
    appname = basename(sevpath);

  re-create:
    while(1)
    {
        waitpid(-1,NULL,WNOHANG);
        appId = getpidbyname(appname);
        if(appId < 0)
        {
            break;
        }       
        fprintf(stderr,"child %s existed,kill it pid=%d\n",appname,appId);
        kill(appId, SIGKILL);
        usleep(500000);
    }

    c_pid = vfork();
    if(c_pid==0)
    {
        execl(apppath,apppath, NULL, NULL);
    }
    else if(c_pid < 0)
    {
        perror("fork");
        return (errno);
    }

    sleep(1);
    while(1)
    {
        ret = waitpid(-1,NULL,WNOHANG);
        if(ret != 0)
        {
            fprintf(stderr,"child exited,go to re-create,errno=%d\n",errno);
            sleep(2);
            goto repeat_create;
        }
        sleep(1);
    }
    return 1;
}

/* my application is under /test/myapp.c */
int main()
{
    int fd;
    fd = open("/dev/my_device", O_RDWR | O_NOFOLLOW, 0644);
    fprintf(stderr,"run my application...\n);
    ioctl(fd, MY_IOCTL_RESET, NULL);
    ...
    close(fd);
    return 0;
}

/* my device driver, will insmod into kernel */
int my_ioctl(struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg)
{
    ...   
    case MY_IOCTL_RESET :                    
        pci_read_config_dword(pdev,...);
        set_current_state(TASK_UNINTERRUPTIBLE);
        WRITE_32(fpga_reset_reg,0x10000);//Reset
        printk("before sleep....\n");
        msleep(5000);
        printk("after sleep....\n");
        pci_write_config_dword(pdev,...);
        my_probe(pdev, NULL);
        set_current_state(TASK_RUNNING);
        printk("reset finished.\n");
        break;
    ....
}

打印出来的日志如下：
run my application...
before sleep....
child exited,go to re-create,errno=10
after sleep....
reset finished.
child myapp existed,kill it pid=1200
child myapp existed,kill it pid=1200
child myapp existed,kill it pid=1200
run my application...
before sleep....
省略。。。


请高手帮忙确认下，是否是一个bug, 或者是我的程序中有什么问题？应该如何正确的实现？谢谢！